Binky

I noticed that my new-to-me 1986 ALAN Record has a slightly flattened oval top tube.
At the front and rear of the bike, where it fits into the seat post lug and head tube lug the top tube is round, and about 1 inch in diameter.

In the middle of the tube the top tube is slightly flattened, and measures about an inch and an eighth wide ( looking down from the top ) and about seven eighths of an inch ( when seen from the side ) at the middle cable guide.

The way the reflected light hits the frame makes the difference obvious. (See picture).

I'm wondering if this is of structural benefit and if it is why isn'y it a more common design feature ?

Bink

caloso

I don't know if it provides any structural benefits, but my cyclocross bike has an ovalized top tube that makes it a bit more comfortable when shouldering.

Binky

Is your top tube oval for its full length and welded in place... or lugged and only flattened in the middle ?
Just curious.

Bink

Andrew R Stewart 

Alans are not welded together. They use an adhesive to join the tubes onto the end junctions (lugs of sorts). The OP states that the tube is rounded at both ends.

Alan did offer a CX frame which, IIRC, had a flattened top tube. perhaps for some reason that model's TT was used on the OP's frame. Andy

ClydeClydeson

There haven't been many aluminum frames made with round cross-section tubes for a long time. Most new bikes have some type of 3D or complicated profile done by 'hydroforming', while old bikes always started with round tubes, and flattening along one axis was the primary strategy to 'tune' tubes for whatever purpose. By the early 90s, most chromoly bikes had similar shaping done to their downtubes, usually flattened width-wise at the head tube and height-wise at the bottom bracket.

Andrew R Stewart 

"I'm wondering if this is of structural benefit and if it is why isn'y it a more common design feature" Bink

In theory a non round tube can have greater bending resistance in the long axis, of an ovalized section of tube, and less so along the short or less wide axis. But remember that the main triangle tubes see a lot of twisting forces, not so much mere bending. The torsional stiffness of an ovalized tube is substantially limited to what a virtual tube would have that has a diameter equal to the shorter axis. (Put another way if a tube is ovalized so it's small axis is half that of the starting round diameter the rotational stiffness will be about 1/4 of the original round tube had. Torsional stiffness has a geometrical relationship with diameter). So ovalizing a main triangle tube has more drawbacks then only the added cost.

Now another reason to ovalize at the ends is to be able to use a larger diameter tube then would fully contact the joining tube. Ovalizing the large tube will allow the joint (welded or brazed)to have complete tube to tube contact and increase the amount of the weld or fillet. As example is a 1.25" top rube joined to a 1.125" seat tube. The sides (or ears of the miter) of the TT will not be touching the ST. By ovalizing the TT vertically the entire TT miter will touch the ST and thus have theoretically more weld/fillet length.

But in real life the differences are fairly minor and the actual welding/filleting skills can be far larger an amount of "change".

It's my opinion that many shaping of tubes is more about branding and marketing then realized strength or stiffness gains. Andy

caloso

I believe mine is hydroformed: it's a more squarish oval at the headtube junction and it flattens out towards the seattube junction. And three sets of cable bosses across the top (rear brake, front and rear derrailleur cables)

icemilkcoffee 

Some bikes in the 80's had tubes which were ovalized in the middle for aerodynamics. Like the Nishiki Aero II I have:

But they were ovalized in the horizontal direction. ie. it's skinny in the horizontal direction and tall in the vertical direction. Your ALAN looks to be opposite of that.
Are you sure it didn't just get squished by a careless mechanic on the bike stand? Are there any other ALAN frames like that?

mrrabbit 

Are those the original recall forks?

Just curious...

=8-|

Binky

That occurred to me so I went online to look at pictures of other ALAN bikes.
I cannot imagine a bike mechanic reefing down on ANY kind of a bike stand clamp with enough force to flatten a bike tube.
Anyway, I found pictures of other ALAN Record frames, as new, on the internet.
Some, but not all, appear to have a flattened top tube. See attached picture from a catalog of some sort.

Bink

Binky

Wow !! Now I'm curious too.
How would I be able to tell ?
Its a ALAN Record made in May, 1986 if that helps.
I traded a Raleigh Grand Prix for this bike to a guy who bought the ALAN second hand off a guy on CraigsList, so the history is a mystery to me.
How can i tell if the forks are, as you call them, the "original recall forks" ?
Does the fork crown appear to be any different from the forks they replaced ?

Bink

easyupbug 

In the old days Park Tools and other stands had levers that could get some serious torque and at a spring setting that worked fine on a gas pipe 1" top tube but could crush a carbon top tube especially a larger diameter if you did not back off the spring tension. To have smashed that Alan tube so beautifully the mechanic would have to have been an artist.

Binky

I just sent off an email to ALAN in Italy with the model and date of manufacture of my bike (May, 1986) and a picture of the frame with a request for information about possible issues or recalls.

Its Sunday so it may be a while before I hear back from them... but I will let you know what (and if) they reply.

I also scoured the internet and the Bike Forums archives to see it it has been an issue. I could find nothing there of note.

What info do you have to share ?

Back soon - I'm off for a ride on the ALAN before it gets too hot.

Bink

gearbasher

I bought an Alan frame, new, back in '88. I don't know when it was manufactured (frame is long gone...cracked seat lug). Anyhow. the top tube was definitely round. I noticed in the pic from the catalogue that the frame shown only has two cable guides on the top tube. Your frame has three and so did mine. Wondering if that matters? As far as the recalled fork, I was told by other riders that the forks with alloy steerers were prone to fail. This was hearsay and I never got any real proof. BTW. Mine had an alloy steerer and I rode it for 45,000+ miles before I noticed the seat lug crack.

Surfer77

Hey Bink!
I just found an Alan like yours, “Record” model, flattened top tube.
Seller lists it as 130mm between dropouts.
I am wondering what your frame measures? 1986 seems early for 130mm, right?
Best,
Robyn

Binky

I just checked mine and the distance between the the rear drops APPEARS to be 125mm or 126mm.... but the rear wheel is not the original.

Bink

fabiofarelli

I got a Super Record, a Record and multiple CX with flattened top tubes.
See part of a catalog from 1983 on the so-called model Sprint (the same as the Super Record) those days.



And far as I know is trouble/recall with Alan frames a myth. The real story was about the Viscount/Lambert fork.
The fork on Binky's Record is the correct fork.

Surfer77

Thank you! Must be 126mm for an 80’s frame. I am quite sure now that the frame I was looking at would have been 126mm as well. I would hesitate to spread it to 130mm because the tubes are only bonded. My 1976 Alan Competition was spread to 126mm, but the brake bridge and chain stay bridge are pinned as well. Very nice Alan Record! Here is my Comp model:

Iride01 

Might be the builder/designer was more interested in what they thought was creating a more aesthetic look and appeal for their customers than a truly beneficial structural design or aerodynamic consideration.

fabiofarelli

screwed and glued. Nice Bike!

Surfer77

Yikes! That is a carbon tube, right?

fabiofarelli

Nope, black anodized. I loosend it myself by heatening (the glue) and unscrewing it. The frame had been damaged and was not usable anymore.

Surfer77

Ah! Thank you! I have heard of carbon tube Alan frames failing, as well as TVTs, but never an aluminium tube frame failing.
-Robyn

Surfer77

Oh, I see you live in Netherlands. I am planning a trip there this June. I am thinking of staying near the Vam Berg and cycling there. I am happy to re-ride the same route, training as opposed to cycle touring. Then visit town for coffee and meals. Hopefully this new covid variant will not be a problem.
-Robyn

fabiofarelli

Drenthe is nice, since a few years we do a ride there, small group, great fun. Nearby the Vam-berg.